1. Field of the Invention
The present invention relates to a plasma processing apparatus. In particular, the present invention relates to a plasma processing apparatus that is used to manufacture a semiconductor device by a technique such as etching a substrate, which is a processing target, or forming a film on the substrate by plasma discharge of a reactive material gas in a sealable chamber, and that is configured so that a plurality of pairs of a cathode electrode and an anode electrode for producing the plasma discharge are disposed in the chamber.
2. Description of the Related Art
U.S. Pat. No. 4,264,393 shows an example conventional plasma processing apparatus for improving etching performance or deposition uniformity according to a plasma chemical technique.
FIG. 7 shows one type of conventional plasma processing apparatus known as a vertical type semiconductor device.
In the semiconductor device manufacturing apparatus shown in FIG. 7, a sealable vertical chamber 11 serves as a reaction container. Anode electrodes 4 are disposed generally perpendicularly to a bottom of the chamber 11 at a central portion of the chamber 11. Each anode electrode 4 is in contact with a heater 14 provided generally perpendicularly to the bottom of the chamber 11 in the central portion of the chamber 11. This heater 14 heats a glass substrate 1 (held by a substrate holding section 15), which is a processing target, to ascertain temperature, e.g., 100° C. to 600° C. This semiconductor device manufacturing apparatus also includes cathode electrodes 2 which are positioned closer to sidewalls of the chamber 11, and which are generally perpendicularly to the bottom of the chamber 10 within the chamber 10.
In the semiconductor device manufacturing apparatus of FIG. 7, anode electrodes 4 and cathode electrodes 2 are arranged to put the cathode electrodes 2 between the anode electrodes 4 (in a state in which two of cathode and anode electrode pairs 7 face each other) at predetermined distances in a horizontal direction. In addition, the semiconductor device manufacturing apparatus of FIG. 7 is configured to produce plasma discharge between the anode electrodes 4 and the cathode electrodes 2, respectively.
The chamber 11 and the anode electrodes 4 consist of stainless steel, aluminum alloy or the like, and ceramics or the like (used as a heat insulating material). Each of the cathode electrodes 2 is arranged to face the substrate 1 at a predetermined distance. Each of the cathode electrodes 2 is supported by a cathode support 5 consisting of insulating glass so as to ensure electrical insulation. The heater 14 is grounded through a grounding terminal 20.
The conventional plasma processing apparatuses have the following disadvantages.
The disadvantages of the apparatus disclosed in the U.S. Pat. No. 4,264,393 will first be described. In this apparatus, a substrate is disposed without distinguishing cathode electrodes from anode electrodes, and a plasma discharge is produced between all adjacent electrodes. Due to this, in terms of film formation, films formed on the cathode electrodes and those formed on the anode electrodes are mixed together. In terms of etching, the substrate etched on the cathode electrodes and that etched on the anode electrodes are mixed up.
Such mixing is not desirable because this disadvantageously results in use of lower-quality films formed on the cathode electrodes and a process onto the anode electrodes unsuited for etching.
In this apparatus, since the distances between the adjacent electrodes are all equal, there is no avoiding producing the plasma discharge, but it is still possible not to use the lower-quality films formed on the cathode electrodes and the process onto the anode electrodes unsuited for etching. Nevertheless, adjacent plasmas interfere with each other because the discharge itself cannot be inhibited, and this results in that the discharge is disadvantageously quite unstable.
The disadvantages of the semiconductor device manufacturing apparatus shown in FIG. 7 will next be described. In the apparatus shown in FIG. 7, it is necessary to control the plasma discharges produced between the two cathode and anode electrode pairs 7 independently of each other so as to provide films uniform in thickness and quality between the respective cathode and anode electrode pairs 7. This disadvantageously requires a wall (corresponding to the heater 14 disposed in the central portion in this example) to prevent the interference of plasmas between the anode electrodes 4. As a result, a configuration of the apparatus is disadvantageously complicated.
Furthermore, if a high frequency power supply such as a radio frequency (RF) power supply is employed in a large-sized apparatus, it is quite difficult to keep the two proximate anode electrodes 4 equal in potential because of radio frequency characteristics (for example, to sufficiently ground them). Due to this, the two proximate anode electrodes 4 tend to interfere with each other, disadvantageously resulting in unstable discharge.
To minimize the influence of the interference, it is necessary to provide an earth wall (the heater 14 in this example) to prevent the interference of plasmas. In this case, the chamber 11 is made large in size, disadvantageously resulting in great cost increase.